JP3825505B2 - Manufacturing method of compound lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a compound lens by forming an aspheric resin layer on the surface of a glass lens.
[0002]
[Prior art]
A compound lens in which an aspherical resin layer is provided on the surface of a glass lens is conventionally known, but there is a limit to the shape of the resin layer that can be molded. For example, as shown in FIG. 2, a molding die 3 having an aspherical molding surface is installed above the glass lens 2, and ultraviolet rays are applied to the ultraviolet curable composition placed in the space therebetween from below the glass lens 2. There is a method of manufacturing by irradiation.
[0003]
Problems of this conventional method will be described below with reference to FIGS. The lower side of the aspherical resin layer shown in FIGS. 3 and 4 is generally a spherical surface, but is a plane for the sake of simplicity of explanation. In the aspherical resin layer shown in FIG. 3, when UV irradiation is performed from the bottom with the same irradiation intensity, the curing reaction proceeds from the lower part 1 d as shown in FIG. 3, and the thinnest part of the aspherical resin layer Even if the polymerization of 1f is completed and the polymerization shrinkage no longer occurs, the polymerization of the thick portion 1e of the aspherical resin layer is in progress. In this state, the polymerization of the thick portion 1e of the aspherical resin layer further proceeds, and even when polymerization shrinkage occurs, the thinnest portion 1f prevents the mold from dropping. Therefore, sink marks (defects in which the resin is separated from the mold and a cavity is generated) occur in the thick portion 1e of the aspheric resin layer.
In order to avoid the above-described thin portion from being cured first, when an ultraviolet ray is irradiated only on the peripheral portion by placing a mask on the thin portion or the like, as shown in FIG. Polymerization progresses first at the peripheral portion 1g and the polymerization shrinkage is completed, but the thin central portion 1h is in an uncured state. In this case, a phenomenon occurs in which the resin layer in the peripheral portion 1g prevents the mold from dropping due to curing shrinkage, and a defect occurs in the central portion 1h.
These are all defects that occur because the shrinkage during the polymerization reaction cannot be controlled. Therefore, conventionally, the aspheric resin layer is likely to be defective, and the yield is extremely poor.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a method capable of efficiently producing a compound lens having an ultraviolet curable aspherical resin layer by reducing the occurrence of defects due to curing shrinkage.
[0005]
[Means for Solving the Problems]
The present invention achieves the above object by controlling the polymerization shrinkage in accordance with the thickness of the aspheric resin layer. That is, in the method for producing a compound lens according to the present invention, an aspheric resin layer is formed by injecting an ultraviolet curable resin composition between a glass lens and a mold having an aspheric molding surface and irradiating with ultraviolet rays. In the method of manufacturing a compound lens, the amount of irradiation light is controlled so that the final stage of polymerization shrinkage is simultaneously performed between the thick and thin portions of the aspheric resin layer to be formed. It is characterized in that the entire portion is polymerized after the thick portion is first shrunk by the difference between the polymerization shrinkage amount and the thin polymerization shrinkage amount.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, as described above, the reaction rate is controlled by increasing the amount of ultraviolet irradiation light where the aspheric resin layer to be formed is thick and decreasing the amount of ultraviolet irradiation light where the layer thickness is thin. By this control, the rate of polymerization shrinkage generated with the reaction is also controlled according to the thickness of the aspheric resin layer to be formed. Furthermore, irradiation control is performed so that the final stage of polymerization shrinkage of the entire resin layer appears almost simultaneously.
Next, the present invention will be described in more detail with reference to the drawings. In the drawings, the aspheric resin layer is shown in an extremely extreme shape for the sake of simplicity.
[0007]
FIG. 1 is an explanatory cross-sectional view of an aspherical resin layer for explaining the progress of the polymerization reaction when irradiated by the method of the present invention, and hence the progress of the polymerization shrinkage. In order to explain the progress of polymerization shrinkage when a single resin layer is formed, it is shown as three layers for convenience. Furthermore, although the lower side of the aspherical resin layer is shown as a plane for the sake of simplicity of explanation, it is generally a spherical surface because it is provided on the spherical surface of the glass lens. That is, an aspheric resin layer is formed between the glass lens 2 and the mold 3 shown in FIG. Since the aspherical resin layer 1 is irradiated with ultraviolet rays from below, the polymerization reaction starts from the lower layer portion 1a and gradually proceeds to the portion 1b and further to 1c.
[0008]
In the present invention, the amount of irradiation light is controlled in accordance with the thickness, so that the polymerization shrinkage rate is cured so as to be uniform throughout, and the concentration of stress due to the curing shrinkage is eliminated. The spherical resin layer can be efficiently manufactured.
As a method for this, the difference between the polymerization shrinkage amount at the thick part of the aspheric resin layer and the polymerization shrinkage amount at the thin part, the thick part is first shrunk and then the whole is polymerized, or the aspheric resin layer is thick. There are a method of making a difference between the polymerization shrinkage rate of a thin film and a polymerization shrinkage rate of a thin part, and a combination thereof.
[0009]
More specifically, an optical member having a characteristic such that the aspherical resin layer has a relative irradiation intensity distribution substantially equal to the desired thickness ratio of the aspherical resin layer is used, and ultraviolet irradiation is performed through this optical member. It is preferable to control the amount of polymerization shrinkage and the rate of polymerization shrinkage.
Examples of the optical member for obtaining the irradiation intensity distribution include a filter, a power lens, and a diffusion plate having a light shielding area.
[0010]
Furthermore, ultraviolet irradiation has been conventionally performed at a high irradiation intensity of 200 mw or more, but at such a high irradiation intensity, the polymerization reaction proceeds rapidly and is difficult to control. However, it has been found that when ultraviolet irradiation is performed with an irradiation intensity of 50 mw or less, the start time and reaction rate of the polymerization reaction can be controlled. That is, at a low irradiation intensity of 50 mw or less, if there is a difference in irradiation intensity between the thick part and the thin part, a large difference occurs in the reaction start time and reaction rate, and eventually the polymerization shrinkage can be controlled.
In the present invention, the irradiation intensity varies depending on the difference in the thickness of the aspherical resin layer and the kind of the resin, but is usually preferably 0.1 to 50 mw, from the viewpoint of easy control of polymerization shrinkage. It is more preferably 1.0 to 20 mw or less, and most preferably 1.0 to 10 mw or less.
[0011]
In the method of the present invention, since the polymerization is performed at a low irradiation intensity as described above, the monomer may remain even when it is recognized that the curing reaction has been completed as a whole. Therefore, it is preferable to complete the polymerization by increasing the irradiation intensity after curing shrinkage is completed, for example, by irradiation with a conventionally employed intensity of 200 mw or more. At this point, due to the curing reaction performed in the previous stage, defects due to stress concentration are not generated even when ultraviolet irradiation is performed with high irradiation intensity.
[0012]
【Example】
Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
[0013]
Example 1
Using a UV curable composition (trade name MP201, manufactured by Mitsubishi Rayon Co., Ltd.) composed of an epoxy acrylate, a polyfunctional acrylate, and a photopolymerization initiator, the start and progress of the polymerization reaction were observed while varying the UV irradiation intensity. FIG. 5 shows changes with time in the voltage (measured with a thermocouple) of the ultraviolet curable composition measured at that time. Since it is known that the reaction calorific value is related to the reaction amount at that time, from the result shown in FIG. 5, a delay in reaction start time and a delay in reaction progress are observed at a low irradiation intensity. It can be seen that the lower the irradiation intensity, the more remarkable. In this experiment, the ultraviolet irradiation intensity distribution is made constant within the measurement area, but it is also possible to provide a two-dimensional intensity distribution and simultaneously control the reaction of each part.
Of the curves shown in FIG. 5, the integrated value of an exothermic curve with an irradiation intensity of 5.0 mw and an exothermic curve with 1.5 mw was obtained as a reaction rate and shown in FIG. As can be seen from FIG. 6, by changing the ultraviolet irradiation intensity according to the layer thickness ratio of the aspherical resin layer, the reaction can proceed at a rate proportional to the thickness between the thick part and the thin part of the resin layer. Accordingly, shrinkage can be generated at the same rate, extreme stress concentration as shown in FIGS. 3 and 4 can be prevented, and a defect-free compound lens can be efficiently molded. it can.
[0014]
Therefore, in order to form the aspherical resin layer (diameter 34 mm) indicated by the curve Asp in FIG. 7, the diameter is formed in the center of the diffusion plate 5 made of polyester resin having a diameter of 35 mm below the glass lens 4 as shown in FIG. A 10 mm aluminum foil 6 affixed is installed, the ultraviolet curable composition is injected between the glass lens 4 and the aspherical mold 8, and the irradiation intensity is 5 mw from the light source 7 through the diffusion plate 5. Upon irradiation, an irradiation intensity distribution curve indicated as “pattern of the present invention” in FIG. 7 was obtained. In FIG. 8, the glass lens 4 is fixed by the lens support member 9, and among the light diffused by the diffusion plate 5, there is also light that is reflected by the lens support member 9 and enters the lens. Despite providing a complete light-shielding portion, a faint irradiation intensity distribution can be obtained as shown in the figure.
The intensity distribution of the ultraviolet ray is determined by the form of the filter for providing the ultraviolet ray irradiation optical system and the intensity distribution, the configuration of the peripheral jig, and the like, and the method for obtaining the intensity distribution is also limited to the configuration of this embodiment. It is not a thing.
When the ultraviolet curable composition was actually irradiated with ultraviolet rays at an irradiation intensity of 5 mw through the diffusion plate and the curing reaction was almost completed, the residual monomer was polymerized by irradiation with an irradiation intensity of 250 mw. An aspheric resin layer having a resin layer thickness indicated by a curve Asp could be formed. In addition, in FIG. 7, the conventional pattern is a pattern when directly irradiating light from a light source without any intervention.
[0015]
In the drawings and the above description, the case where an aspherical resin layer having a thick peripheral portion and a thin central portion has been described. However, the present invention is not limited to this shape, and the peripheral portion is thin and the central portion is formed. It can be applied to other shapes such as a thick aspherical resin layer.
[0016]
【The invention's effect】
According to the present invention, since the polymerization shrinkage when forming the aspheric resin layer can proceed according to the layer thickness, the concentration of partial stress due to the polymerization shrinkage can be prevented, resulting in the stress concentration. There is little occurrence of defects such as distortion. In addition, polymerization shrinkage can be easily controlled by the amount of irradiation light, and a composite lens having an aspheric resin layer can be efficiently manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view of an aspherical resin layer for explaining the progress of a polymerization reaction when irradiated by the method of the present invention, and hence the progress of polymerization shrinkage.
FIG. 2 is a cross-sectional view of a molding die for forming an aspheric resin layer.
FIG. 3 is an explanatory diagram of a state of forming an aspheric resin layer by a conventional method.
FIG. 4 is an explanatory diagram of a state of forming an aspheric resin layer by a conventional method.
FIG. 5 is a graph showing a change with time of reaction heat of an ultraviolet curable composition at a slight ultraviolet irradiation intensity measured in an example of the present invention.
6 is a graph showing the reaction rate of the integrated values of the irradiation intensity 5.0 mw curve and 1.5 mw curve shown in FIG.
FIG. 7 is a graph showing a target aspheric resin layer in an example and an irradiation intensity distribution generated in the example.
FIG. 8 is an explanatory diagram showing an example of a method for manufacturing a compound lens according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aspherical resin layer 2 Glass lens 3 Mold 4 Glass lens 5 Diffuser 6 Aluminum foil 7 Light source 8 Aspheric mold 9 Lens support member

Claims (1)

In a method for producing a compound lens by injecting an ultraviolet curable resin composition between a glass lens and a mold having an aspheric molding surface and irradiating with ultraviolet rays to form an aspheric resin layer The amount of irradiation is controlled so that the final stage of polymerization shrinkage is performed simultaneously at the thick and thin portions of the aspheric resin layer, and the polymerization shrinkage amount at the thick and thin portions of the aspheric resin layer is controlled. A method of manufacturing a compound lens, wherein the entire portion is polymerized after the thick portion is first shrunk by the difference.

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